Test the trace simulator with CCNOT decompositions

See
microsoft/qsharp-runtime#1038

mcx/qsharp/ResourcesEstimator.cs

@@ -2,7 +2,7 @@
 using System.Threading.Tasks;
 using System.Collections.Generic;
 using Microsoft.Quantum.Simulation.Simulators.QCTraceSimulators;
-using ClassiqChallenge;
+using TestTraceSimulator;
 
 namespace host
 {
@@ -12,31 +12,28 @@ static class Program
 
         // See:
         // https://docs.microsoft.com/en-us/dotnet/api/microsoft.quantum.simulation.simulators.qctracesimulators.qctracesimulatorconfiguration
-        static QCTraceSimulatorConfiguration GetConfig()
+        static QCTraceSimulatorConfiguration GetConfig(bool tDepth = false)
         {
             var config = new QCTraceSimulatorConfiguration();
             config.UseWidthCounter = true;
             config.UseDepthCounter = true;
 
-            // Optimize for using less qubits
-            config.OptimizeDepth = false;
+            // Optimize for minimal depth
+            config.OptimizeDepth = true;
 
             // Configure depth counting:
             // Count every relevant primitive in the depth metric.
             // By default only T primitives are counted, i.e. the depth is T-depth.
-            foreach (var primitive in new List<PrimitiveOperationsGroups>{
-                PrimitiveOperationsGroups.CNOT,
-                PrimitiveOperationsGroups.QubitClifford,
-                PrimitiveOperationsGroups.R,
-                PrimitiveOperationsGroups.T,
-                }
-            )
+            if (!tDepth)
             {
-                config.TraceGateTimes[primitive] = DefaultPrimitiveDepth;
+                foreach (var primitive in Enum.GetNames<PrimitiveOperationsGroups>())
+                {
+                    config.TraceGateTimes[Enum.Parse<PrimitiveOperationsGroups>(primitive)] =
+                    DefaultPrimitiveDepth;
+                }
             }
-            // Do not count measurements - they are only helpers in this case.
-            config.TraceGateTimes[PrimitiveOperationsGroups.Measure] = 0;
 
+            Console.WriteLine("Primitives depth:");
             foreach (var kvp in config.TraceGateTimes)
             {
                 Console.WriteLine(kvp);
@@ -48,17 +45,29 @@ static QCTraceSimulatorConfiguration GetConfig()
         // https://docs.microsoft.com/en-us/azure/quantum/machines/qc-trace-simulator/width-counter
         static async Task Main(string[] args)
         {
-            var sim = new QCTraceSimulator(GetConfig());
+            var tDepth = false;
 
-            var singleQubitResult = await ApplyMultiControlledX.Run(
-                sim, initControl: false, initTarget: false
-            );
+            if (args.Length > 0)
+            {
+                tDepth = args[0] == "--t-depth";
+            }
 
-            double width = sim.GetMetric<ApplyMultiControlledX>(MetricsNames.WidthCounter.ExtraWidth);
-            double depth = sim.GetMetric<ApplyMultiControlledX>(MetricsNames.DepthCounter.Depth);
+            var config = GetConfig(tDepth: tDepth);
+            var simOriginal = new QCTraceSimulator(config);
+            var simNonOriginal = new QCTraceSimulator(config);
 
-            Console.WriteLine($"Single qubit result: {singleQubitResult}");
-            Console.WriteLine($"Width: {width}, Depth: {depth}.");
+            await Task.WhenAll(
+                TestCCNOT.Run(simOriginal, original: true),
+                TestCCNOT.Run(simNonOriginal, original: false)
+            );
+
+            foreach (var sim in new List<QCTraceSimulator> { simOriginal, simNonOriginal })
+            {
+                double depth = sim.GetMetric<TestCCNOT>(MetricsNames.DepthCounter.Depth);
+                double width = sim.GetMetric<TestCCNOT>(MetricsNames.WidthCounter.ExtraWidth);
+                Console.WriteLine(sim.Name);
+                Console.WriteLine($"Depth: {depth}, width: {width}.");
+            }
         }
     }
 }

mcx/qsharp/TestCCNOT.qs

@@ -0,0 +1,39 @@
+namespace TestTraceSimulator {
+    open Microsoft.Quantum.Intrinsic;
+
+    // See:
+    // https://github.com/microsoft/qsharp-runtime/blob/1761b379397520c0fa10ec8d2592f1df2b1acecf/src/Simulation/TargetDefinitions/Decompositions/CCNOTFromCCZ.qs#L22-L31
+    operation CCNOTFromCCZ(control1 : Qubit, control2 : Qubit, target : Qubit) : Unit {
+        within {
+            H(target);
+        }
+        // The internal `CCZ` operation:
+        // https://github.com/microsoft/qsharp-runtime/blob/1761b379397520c0fa10ec8d2592f1df2b1acecf/src/Simulation/TargetDefinitions/Decompositions/Utils.qs#L101-L116
+        apply {
+            Adjoint T(control1);
+            Adjoint T(control2);
+            CNOT(target, control1);
+            T(control1);
+            CNOT(control2, target);
+            CNOT(control2, control1);
+            T(target);
+            Adjoint T(control1);
+            CNOT(control2, target);
+            CNOT(target, control1);
+            Adjoint T(target);
+            T(control1);
+            CNOT(control2, control1);
+        }
+    }
+
+    operation TestCCNOT(original : Bool) : Unit {
+        use (control1, control2, target) = (Qubit(), Qubit(), Qubit());
+        if original {
+            CCNOT(control1, control2, target);
+        }
+        else {
+            CCNOTFromCCZ(control1, control2, target);
+        }
+    }
+
+}